Baseline data for Andean paleomobility research: a radiogenic strontium isotope study of modern Peruvian agricultural soils

Abstract

While the use of radiogenic strontium isotope values to examine paleomobility is increasingly common in the Andes, and beyond, many questions about baseline variability remain. To better understand baseline radiogenic strontium isotope compositions in the Andes, we present new 87Sr/86Sr values from Peruvian soil samples. Modern soil samples were collected from agricultural fields from the following areas in central and southern Peru: Arequipa, Atico, Camana, Chala, Cusco, Ica, Ilo, Lima, Mejia, Moquegua, Nazca, Ocona, Palpa, Pisco, Puno, Tacna, and Yauca. Samples were partially dissolved to better approximate the bioavailable strontium. Radiogenic strontium isotope values from the partially dissolved soil samples range from 87Sr/86Sr = 0.70202 to 0.71894 and, for all soil samples, have a mean of 87Sr/86Sr = 0.70773 ± 0.00166 (1σ, n = 114). In general, the 87Sr/86Sr values measured for soil samples collected from modern agricultural fields reflect the expected 87Sr/86Sr values based on bedrock geology. Comparing our new soil data with published radiogenic strontium isotope data for bedrock, soil, water, and faunal samples provides constraints on the regions in the Andes that can, and cannot, be distinguished through radiogenic strontium isotope analysis.